Manufacture of coated materials and product



March 24?, 19 42.

A. o. BECKMAN ET AL 2,277,287

MANUFACTURE OF COATED MATERIALS AND PRODUCT Filed Feb. 4, 1959 Patented Mar. 24, 1942 MANUFACTURE or cons!) lua'ranms AND raonuo'r Arnold o. Beckman, Altaflena, and William A.

Bush, and Harry Rubin, Los Angeles, Calif.

Application February 4, 1939, Serial No. 254,680

6 Claims.

This invention relates to the manufacture of' a suitable wrapping material useful in the wrapping of such commodities as'bread. In wrapping bread, as well as other like products, a substantially transparent yet relatively inexpensive wrapper is required. Such a wrapper should de-- sirably be heat sealing so that it can be wrapped cheaply. It should also be relatively stable over a long period of time, so that the wrappers can be made up and stored in quantities.

It is in general the broad object o! the present invention to provide for the transparentizing of a suitable paper base and this with a composition which can be heat sealed and which is neverthe-- less so non-tacky that it can be'stored in piles under pressure without adjacent sheets sticking together. This last property is known as nonblocking."

-In accordance with the present invention we have determined that a paper is readily transparentized and coated .if a plurality of coats are applied thereto. To this end we preferably first apply to the paper a tacky coating (preferably having substantially the same index of refraction as the base sheet) and then anon-tacky coating as the outer surface coat. The non-tacky coat-' ing protects goods and adjacent sheets against the tacky coating, while disruption of the nontacky coating permits the tacky coating to be employed for heat sealing and like purposes.

Briefly summarizing. the tacky -undercoat' serves the following purposes:

(0) Having approximately the same index of" refraction as cellulose it makes the paper transparent. 1

(1)) Being permanently tacky, it seals mostcoatings that are desirable in every respect but that of adhering to the paper.

(c) Being permanently tacky it lends to the paper the property of heat sealing if the surface coat is destroyed in any way, i. e., chemically by chemical reaction of solution, physically by scraping, rubbing, or heat.

(d) If applied at a temperature above the boiling point of water, it displaces mostof the water inthe sheet and will, therefore, keep the sheet' from becoming brittle even when subjected to higher temperatures almost but not quite sumcient to decompose the paper, and also due to this property of displacement and due to the 'water resistance of the substance itself it lends (or fwhiskers"), tying them down for the covering action of the secondor top coat, thus preventing the formation of wicks.

(f) It limits the quantity of the top coat which can and need be applied.

. The non-tacky top coat serves the following purposes:

(a) Keeps the tacky-undercoat from blocking the sheets. 4

. (b) Provides asurface which has a high gloss.

(c) Provides a surface which oan'be printed upon by most inks that do not dry by penetration.

(d) Provides a surface which. will heat seal paper on itself.

(e) Aids in the waterproofing of the sheet, because of its wax oil and cellulose ether components and moistureproofing due to the wax glossy appearance.

(h) Completes the process of transparentizing by leveling the surface and making it homogeneous, thus not refracting the light in all directions, but allows the light to pass through in parallel beams.

As a suitable first coating, we have successfully employed such materials as a mineral oil (a highly refined paramn hydrocarbon having a 7 small, if any, sulfonatable residue): a paraflin wax: a mixture of mineral oil and rosin, varying between ,mineral 011 down to mineral oil with the balance rosin. If dimculty is encountered due to oxidation, an anti-oxidant such as hydroquinone can be added, usually 0.5%-1% of this sufiicing. We have also successfully employed Staybelite, a; hydrogenated rosin made by Hercules Powder Company. This we have employed with a mineral oil in the proportions of from 0% to 70% of the rosin, the balance being mineral oil to which may be added a small amount of an anti-oxidant such as hydroquinone. We have also employed castor oil. and talloel a product sometimes referred to as liquid rosin). Almost any vegetable oil can be used if it is of sumcient clarity. Because of the susceptibility of vegetable oils tooxldation, it is desirable that anti-oxidants be employed.

For greatest. durability we prefer to use a mixture of Staybelite and castor oil, or castor oil product of a bleached refined castor oil and ufactured by California Flaxseed Company as castor oil phthalate, as #91, a synthetic plastlcizer composed mainly (78%) of a condensation product of bleached refined castor oil and phthalic anhydrlde.

We have also successfully used Pllolite dissolved in liquid petrolatum as a first coating, particularly where a very high resistance to moisture vapor penetration is desirable.

As the top coating or outer coating, the following constituents can be employed:

l. A compatible or partially compatible resin. As asuitable composition we have made up one comprising from to 75% of natural gum resin modified by a glycerin-olefin-dicarboxylic acid ester in the proportions of 21% of the former to 29% of the latter components. Such a resin is that known as #225, manufactured by California Flaxseed Company. Instead of #225, a

resin known as #157, manufactured by Cali-' fornia Flaxseed Company can be employed. This resin is composed of rosin reacted with glycerol in the ratioof 90.8% rosin to 9.2% glycerin, to the point where the acid number is from 11 to 13. Its softening point is 190 F. and the melting point is 195 F. It is commonly known as estergum.

The above indicate the characteristics of the resins included in the composition. Various other suitable equivalent resins can be employed. Circular No. 545 of National Paint, Varnish and Lacquer Association lists some hundred-odd resins and gives their compatibility with ethyl cellulose.

2. A cellulose ether, such as ethyl cellulose,

from 9% to 25%. In place of ethyl cellulose, anyother suitable cellulose ether can be employed, such as benzyl cellulose, or ethyl benzyl cellulose. 3. A wax compatible or partly compatible with the cellulose ether employed. Such a wax is candelilla wax. This is included to the extent of from 0% to 12%. Utilized to this extent, a glass clear film will be secured. Greater percentages can be employed if the clarity and gloss of the film can be diminished. Montan wax can be used in the same percentage as candelilla wax.

4. A plasticizing agent such as castor oil or talloel from 0% to 25% for the castor oil and from 0% to for the talloel.

The following materials, of minor import, can be employed to advantage:

5. Incompatible ingredients are added to reduce the melting point of the mixture to aid in its manufacture and application to a base sheet,

and to lubricate the surface so that the surface phthalic anhydride. Such a product is that man-- tion. A sufficient quantity of anti-oxidants, usually a quantity of the order of 1%, is employed to prevent undue brittleness and loss of heat-sealing properties and provide a careful control of oxidation.

7. A resinous acid. Rosin or hydrogenated rosin can be employed to provide this constituent. In the case of some resins, such as the #225, not completely compatible, the addition of up to 10% of the total mass of a resinous acid will cause the mixture to become homogeneous and compatible. The amount of resin acid used depends on the compatability of the difiiculty soluble resin employed. Rosin can be employed for this because of its high abietic acid content.

8. A fatty acid such as the linseed oil fatty acids or perilla oil fatty acids, or other suitable high molecular weight fatty acids. If linseed oil is used in the mixture it will be partly incompatible with thecellulose ether, but addition of 3% of a fatty acid makes the mixture compatible and homogeneous. This applies to many vegetable oils which may be used as plasticizing agents and their fatty acids.

The following are listed as compositions which have been employed successfully and which embody the present invention:

Per cent #225 50 Rosin 8.3 Candelilla wax 7.5 Low melting point paraffin wax 7.5 Mineral oil 'l. 5 Bleached refined castor oil 10 This composition ages somewhat rapidly but is otherwise useful.

feels smooth and non-tacky. For this purpose,

used when the resin has a readily oxidizable portion and the oxidation products are insoluble and infuslble in the rest of the component. Such a product is the #225 resin aforementioned; this resin, having a non-reacted double bond, is susceptible to chemical action, particularly oxida- Per cent Ethyl cellulose i2 Castor oil bleach, ref 12 Mineral oil 5 Candelilla wax s 12 Staybelite 10 #157 20 #225 28 Hydroquinone 1 This composition ages fairly well.

?arts Ethyl cellulose 25 Castor oil 20 Candelilla wax #225 a 25 This composition is very tough and flexible and can be produced with a high gloss.

The preferred composition is as follows:

Per cent High visc. ethyl cellulose 15 Castor oil bleached,'refined l5 Candelilla wax "a"--- 15 #225 55 This composition would not heat seal #2 glassine by itself, but did heat seal it when applied over the tacky impregnated paper.

The following composition was employed:

Percent Ethyl cellulose 22 Rosin W 55 Montan wax bleached 23 It resulted in a cloudy cake that was quite flexible. It provides an opaque coat as will'be presently explained.

It was found that the tolerance for waxes in these compositions varied from about 10% for bath and the tension remove montan wax to almost 20% for candelilla wax. The tolerance refers to the amount of wax being added to the composition before the film became cloudy.

Percent Ethyl cellulose, medium viscosity Candelilla wax Castor oil bleached, refined 5 #157 30 X rosin 30 This -composition has a very slight cloudtears paper on heat seal, has fair gloss, does not fly from paper when rattled, does not block when subjected to 3 lb. pressure per sq. in. over a period of 8 days with intermittent inspection, and is quite flexible.

In case an opaque coating is desired, this can be produced by using a very high wax content, in which case the opaqueness is due to the wax. Waxes tend to crystallize in the coating, and thus render the mass opaque. Pigments can also be incorporated, as can dyes, so that almcst any color can be obtained.

In the drawing accompanying and forming a part hereof, Figures 1 and 2 respectively provide schematic representations of the apparatus and steps employed in applying the first and second coats. 1

In applying the material, the paper to be coated is preferably first run from a roll 2 through a bath of the first coating composition carried in a tub or vessel 3. The bath is usually heated to a temperature of 180 to 212 F. so that the composition fiows readily. At the higher temperature water is driven out of the base sheet. A smoothing rod or drag dis employed to adjust tension on the paper base sheet. The heated moisture and entrained air from the sheet which is subject to the bath and penetration of the coating material for from 5 to 20 minutes. The material is wound up on reel 6 which is either used as a storage reel or else a feed reel for the second or top coating. Thereafter rial, the coated sheet, on into the operation for applying the second coating. Referring to Figure 2, reel 5 carrying a suitable supply of paper preferably, though not necessarily pre-coated with the tacky l and 8. Roll 1 is heated to about 210 F., preferably just below 212 F. Beneath it a heated drip pan, F., is provided. I, is fed on between roll 8, usually made of The material, passing over roll move any excess. Roll 1 is slightly below roll 8 so that excess material drains toward roll I.

The hot sheet then passes on between hot metal rolls 9, where the second coating composition. is applied. The molten material to be applied to the paper or base sheet as a second coat, at a temperature of about 340 F., is fed on from feed means II. The rolls 9 are at about 340. F., they serve to apply a thin coat of the material to the base sheet. The feeding means i I includes orifices releasing the coating composition from a constant level reservoir, so that the coating material is fed at a uniform rate. A substitute for the means II, which may be preferred, would be to dip the sheet into a suitable vessel of the sec ond coating material, under a conventional smoothing roll or drag, and from thence drawit between the hot metal rolls 9. It will be apprecireel 5 is utilized to feed the matebase, feedsthe sheet between rolls this roll and an unheated Neoprene and Thiokol. These serve to smooth out the first coat and re-- heated to a temperature of -210 but permits it to pass in parallel beams.

ated that there are many mechanical means which can be used with substantially equal emcacy, hence the means shown and described are to be deemed illustrative only. The thickness of the coating is determined (1) by the length of time which the base sheet is in contact with the coating material, 2) the temperature and (3) the pressure applied by rolls 9, and (4) the amount of the previous tacky material applied to the surface. By regulating these various factors the thickness of the material on the base sheet. after application of the first tacky coating, can be regulated.

From the hot metal roll 9 the coated sheet passes over an ironing roll i2, and a second ironing roll i4. These run at a rate faster than that at which the coated base material moves, to iron the material, apply a gloss and smooth surface to it, at a temperature of about 240 F., ironing out inequalities, making the coating homogeneous whereby it does not refract light in all directions It is placed'so that the material is not positively engaged, but is by the rolls. Thereafter the material is passed over a roll it and onto the roll of finished coated material being assembled.

We claim:

1. In the manufacture of a coated structure from an impregnatable base sheet having a surface, the steps of applying to said surface a first coating of rosin dissolved in a non-volatile oil, said first coating being tacky when cold and being applied at a temperature whereat said material is a liquid and moisture in said base is substantially eliminated, and applyingto said surface,'coated as aforesaid, a second coating composed mainly of a natural resin acid-glycerin reaction product with ethyl cellulose dissolved therein, said second coating being miscible with said first coating on said base sheet to provide a normally non-tacky coated surface but which, upon localized heat application, is capable of bonding to itself, said second coating being applied in a molten condition and at a temperature whereat it mixes with said first coating on said surface, and thereafter ironing the coated sheet at an elevated temperature to iron out inequalities and homogenize the applied coatings.

2. In the manufacture of a coated structure from an impregnatable base sheet, the steps of applying to the base as a first coating a heated material fluid but stable at an elevated temperature of application of about 200 F. and which penetrates said base and is normally tacky when cold, said first coating material comprising rosin dissolved in a non-volatile oil, applying to said base, coated as aforesaid, as a second coating a heated material fiuid but stable at an elevated temperature of application of about 300 F. and

compatible and miscible with said first coating on said sheet and normally non-tacky when cold, said second coating comprising ethyl cellulose and a resin in which ethyl cellulose is soluble,

- and heating the sheet, coated as aforesaid to homogenize said coatings.

3. In the manufacture of a coated structure from an impregnatable base sheet having a surface, the steps of applying to said surface a first coating of a material comprising rosin dissolvednevertheless smoothed and-ironed 4. In the manufacture of a coated structure from an impregnatable base sheet having a surface, the steps of applying to said surface a first coating of rosin dissolved in castor oil as a solvent, said first coating being tacky when cold and being applied at a temperature whereat said material is a liquid and moisture in said base is substantially eliminated, and applying to said surface, coated as aforesaid, a second coating composed of about 55% of ester gum, about 20% ethyl cellulose and about 25% wax and miscible with said first coating on said base sheet to provide a normally non-tacky coated surface but which, upon localized heat application, is capable of bonding to itself, said second coating being applied in a molten condition and at a temperature whereat it mixes with said first coating on said surface, and thereafter ironing the coat- ,edsheet at an elevated temperature to iron out inequalities and homogenize the applied coatings.

- tion and at whereat it 5. In the manufacture of a coated structure from an impregnatable base sheet having a surface, the steps of applying to said surface a first coating of rosin dissolved in castor oil as a solvent, said first coating being tacky when cold and being applied at a, temperature of about 200 F., and applying to said surface, coated as aforesaid,v a second coating composed of about 55% of ester gum, about 20% ethyl cellulose and about 25% wax and miscible with said first coating on said base sheet to provide a normally non-tacky coated surface but which, upon localized heat application, is capable of bonding to itself, said second coating being applied in a molten condimixes with said first coating on said surface, and thereafter ironing the coated sheet .at an elevated temperature to iron out inequali- L ties and homogenize the applied coatings.

6. A paper sheet impregnated with a first tacky coating of rosin dissolved in a non-volatile oil and a second non-tacky coating composed mainly of a natural resin acid-glycerin reaction product with ethyl cellulose dissolved therein, said coatings being at least partially homogenized to ensure that said sheet is translucent, nontacky and non-blocking but, upon localized heat application, is heat scaling to itself.

' ARNOLD o. BECKMAN.

wnmu A. BUSH.

a temperature of about 300 F. and 

